Process for the preparation of substituted cyclopropanecarbaldehydes

ABSTRACT

The invention relates to a process for the preparation of cyclopropanecarbaldehydes of formula ##STR1## in which R 1  is C 1  -C 4  alkyl or benzyl, which comprises (a) reacting a tetrahydrofuran of formula ##STR2##  in which X is halogen and R 2  is unsubstituted or halo-substituted C 1  -C 10  alkyl, C 3  -C 6  -cycloalkyl that is unsubstituted or substituted by halogen, C 1  -C 4  alkyl or by C 1  -C 4  alkoxy, or phenyl or benzyl each of which is unsubstituted or substituted by halogen, C 1  -C 4  alkyl, C 1  -C 4  alkoxy, nitro or cyano, with a halogenating agent to form a 1,2,4-trihalobutyl ether of formula ##STR3##  in which X is halogen and R 2  is unsubstituted or halo-substituted C 1  -C 10  alkyl, C 3  -C 6  cycloalkyl that is unsubstituted or substituted by halogen C 1  -C 4  alkyl or by C 1  -C 4  alkoxy, or phenyl or benzyl each of which is unsubstituted or substituted by halogen, C 1  -C 4  alkyl, C 1  -C 4  alkoxy, nitro or cyano, and 
     (b) then reacting the compound of formula III with an aqueous bisulfite solution to form a bisulfite adduct of formula ##STR4##  in which X is a halogen and Y is a cation equivalent of an alkali metal or alkaline earth metal ion, and 
     (c) then cyclising the adduct, in the presence of a base, with a thiolate of formula 
     
         R.sub.1 --S.sup.⊖  Z.sup.⊕                     (V) 
    
      in which R 1  is C 1  -C 4  alkyl or benzyl and Z is a cation equivalent of an alkali metal or alkaline earth metal ion, to form a cyclopropanecarbaldehyde of formula I, and to the individual Process Steps (a), (b) and (c) and the combinations thereof (a)+(b) and (b)+(c), and to the novel intermediates of formulae III and IV.

The invention relates to a novel process for the synthesis of1-alkylthio- and 1-benzylthio-substituted cyclopropanecarbaldehydes offormula ##STR5## in which R₁ is C₁ -C₄ alkyl or benzyl.

The cyclopropanecarbaldehydes of formula I are valuable intermediatesfor the synthesis of agrochemical active substances. They are valuable,for example, for the preparation of the cycloalkanecarbaldoximecarbamates known from DE-A-21 20 908 and for the synthesis of the2-acyl-cyclohexane-1,3-diones having herbicidal and plantgrowth-regulating activity described in EP-A-O No. 243 313.

Those cyclohexanediones are substituted inter alia in position 5 by a1-alkylthio- or a 1-benzylthio-cycloprop-1-yl radical. They may beprepared by a malonic ester synthesis starting from 1-alkylthio- or1-benzylthio-cyclopropanecarboxaldehydes, respectively. In that process,first of all the aldehyde is condensed with acetone to form thecorresponding 4-(1-alkyl-(or benzyl-)thio)-cyclopropyl-but-3-en-2-onewhich is subsequently cyclised to form the cyclohexanedione usingmalonic ester or cyanoacetic acid ester. The cyclohexanedione obtainablein this manner is then functionalised in position 2 in a manner knownper se.

A process for the preparation of compounds of formula I in which R₁ isC₁ -C₄ alkyl is known from DE-A-2 120 908. In that five-step process,chloroacetonitrile is reacted by way of alkylthioacetonitrile to form a1-alkylthiocyclopropanecarbonitrile. That compound is then hydrolysed,converted first into the acid chloride and then into an amide, andreduced to the aldehyde by means of LiAlH₄.

This process has numerous disadvantages. Apart from the poor total yieldof the process, complex process steps are necessary for the individualstages of the reaction. Moreover, the alkylthioacetonitrile required asstarting compound is corrosive and irritating to the eyes.

In contrast to that process, the invention relates to a process for thepreparation of cyclopropanecarbaldehydes of formula ##STR6## in which R₁is C₁ -C₄ alkyl or benzyl, which comprises

(a) reacting a tetrahydrofuran of formula ##STR7## in which X is halogenand R₂ is unsubstituted or halo-substituted C₁ -C₁₀ alkyl, C₃ -C₆-cycloalkyl that is unsubstituted or substituted by halogen, C₁ -C₄alkyl or by C₁ -C₄ alkoxy, or phenyl or benzyl each of which isunsubstituted or substituted by halogen, C₁ -C₄ alkyl, C₁ -C₄ alkoxy,nitro or cyano, with a halogenating agent to form a 1,2,4-trihalobutylether of formula ##STR8## in which X is halogen and R₂ is unsubstitutedor halo-substituted C₁ -C₁₀ alkyl, C₃ -C₆ cycloalkyl that isunsubstituted or substituted by halogen, C₁ -C₄ alkyl or by C₁ -C₄alkoxy, or phenyl or benzyl each of which is unsubstituted orsubstituted by halogen, C₁ -C₄ alkyl, C₁ -C₄ alkoxy, nitro or cyano, and

(b) then reacting the compound of formula III with an aqueous bisulfitesolution to form a bisulfite adduct of formula ##STR9## in which X ishalogen and Y is a cation equivalent of an alkali metal or alkalineearth metal ion, and

(c) then cyclising the adduct, in the presence of a base, with athiolate of formula

    R.sub.1 --S.sup.⊖ Z.sup.⊕                      (V)

in which R₁ is C₁ -C₄ alkyl or benzyl and Z is a cation equivalent of analkali metal or alkaline earth metal ion, to form acyclopropanecarbaldehyde of formula I.

Process steps (a), (b) and (c) are novel. The invention relates to thecombination of all three process steps, as described hereinbefore, tothe combination of the process steps (a)+(b), and (b)+(c), and to theindividual steps (a), (b) and (c) on their own.

The 1,2,4-trihalobutyl ethers of formula III and the bisulfite adductsof formula IV are also novel and the present invention relates to thosealso.

The invention thus relates to the novel 1,2,4-trihalobutyl ethers offormula ##STR10## in which X is halogen and R₂ is unsubstituted orhalo-substituted C₁ -C₁₀ alkyl, C₃ -C₆ cycloalkyl that is unsubstitutedor substituted by halogen, C₁ -C₄ alkyl or by C₁ -C₄ alkoxy, or phenylor benzyl each of which is unsubstituted or substituted by halogen, C₁-C₄ alkyl, C₁ -C₄ alkoxy, nitro or cyano, and to the novel bisulfiteadducts of formula ##STR11## in which X is halogen and Y is a cationequivalent of an alkali metal or alkaline earth metal ion.

The tetrahydrofurans of formula II are valuable starting compounds forthe process according to the invention. Some of these compounds areknown from the literature. The compounds of formula II can be preparedanalogously to processes known from the literature. The alcoholysis of2,3-dihalotetrahydrofurans [M. Holik et al.; (Chem. Zvesti; 25 (1971),9); V. Zezula and M. Kratochvil; Collect. Czech. Chem. Commun.; 35(1970), 1745], [L. M. Bolotina et al.; Khim. Geterotsikl. Soedin; 4(1968), 200], for example, provides a convenient route to this class ofcompounds. The Zn- or ZnCl₂ -catalysed addition of oxiranes to2,3-dichlorotetrahydrofuran or mixtures of 2,3-dichlorotetrahydrofuranwith tetrahydrofuran is another convenient method of producing 2-[2- or4-chloroalkyl-substituted]-3-chlorotetrahydrofurans of formula II [M.Kratochvil, Collect. Czech. Chem. Commun. 25 (1960), 1353].

The invention also relates to the novel tetrahydrofurans of formula II##STR12## in which X is halogen and R₂ is unsubstituted orhalo-substituted C₁ -C₁₀ alkyl, C₃ -C₆ cycloalkyl that is unsubstitutedor substituted by halogen, C₁ -C₄ alkyl or by C₁ -C₄ alkoxy, or phenylor benzyl each of which is unsubstituted or substituted by halogen, C₁-C₄ alkyl, C₁ -C₄ alkoxy, nitro or cyano, with the proviso that when Xis chlorine R₂ is not unsubstituted C₁ -C₆ alkyl, cyclohexyl, C₄ -C₁₀alkyl substituted in the 2 position by chlorine, or 4-chlorobutyl, andthat when X is bromine or iodine R₂ is not C₁ -C₄ alkyl.

The individual Process Steps of the invention, and combinations thereof,are defined as follows:

Two-step processes:

The process for the preparation of cyclopropanecarbaldehydes of formula##STR13## in which R₁ is C₁ -C₄ alkyl or benzyl, which comprises

(b) reacting a 1,2,4-trihalobutyl ether of formula ##STR14## in which Xis halogen and R₂ is unsubstituted or halo-substituted C₁ -C₁₀ alkyl, C₃-C₆ cycloalkyl that is unsubstituted or substituted by halogen, C₁ -C₄alkyl or by C₁ -C₄ alkoxy, or phenyl or benzyl each of which isunsubstituted or substituted by halogen, C₁ -C₄ alkyl, C₁ -C₄ alkoxy,nitro or cyano, with an aqueous bisulfite solution to form a bisulfiteadduct of formula ##STR15## in which X is halogen and Y is a cationequivalent of an alkali metal or alkaline earth metal ion and

(c) subsequently cyclising the adduct, in the presence of a base, with athiolate of formula

    R.sub.1 --S.sup.⊖ Z.sup.⊕                      (V)

in which R₁ is C₁ -C₄ alkyl or benzyl and Z is a cation equivalent of analkali metal or alkaline earth metal ion, to form acyclopropanecarbaldehyde of formula I;

and the process for the preparation of a bisulfite adduct of formula##STR16## in which X is halogen and Y is a cation equivalent of analkali metal or alkaline earth metal ion, which comprises

(a) reacting a tetrahydrofuran of formula ##STR17## in which X ishalogen and R₂ is unsubstituted or halo-substituted C₁ -C₁₀ alkyl, C₃-C₆ -cycloalkyl that is unsubstituted or substituted by halogen, C₁ -C₄alkyl or by C₁ -C₄ alkoxy, or phenyl or benzyl each of which isunsubstituted or substituted by halogen, C₁ -C₄ alkyl, C₁ -C₄ alkoxy,nitro or cyano, with a halogenating agent to form a 1,2,4-trihalobutylether of formula ##STR18## in which X is halogen and R₂ is unsubstitutedor halo-substituted C₁ -C₁₀ alkyl, C₃ -C₆ -cycloalkyl that isunsubstituted or substituted by halogen, C₁ -C₄ alkyl or by C₁ -C₄alkoxy, or phenyl or benzyl each of which is unsubstituted orsubstituted by halogen, C₁ -C₄ alkyl, C₁ -C₄ alkoxy, nitro or cyano, and

(b) then reacting the compound of formula III with an aqueous bisulfitesolution to form the bisulfite adduct of formula IV.

Single-step processes:

The process for the preparation of 1,2,4-trihalobutyl ethers of formula##STR19## in which X is halogen and R₂ is unsubstituted orhalo-substituted C₁ -C₁₀ alkyl, C₃ -C₆ -cycloalkyl that is unsubstitutedor substituted by halogen, C₁ -C₄ alkyl or by C₁ -C₄ alkoxy, or phenylor benzyl each of which is unsubstituted or substituted by halogen, C₁-C₄ alkyl, C₁ -C₄ alkoxy, nitro or cyano, which comprises

(a) reacting a tetrahydrofuran of formula ##STR20## in which X ishalogen and R₂ is unsubstituted or halo-substituted C₁ -C₁₀ alkyl, C₃-C₆ -cycloalkyl that is unsubstituted or substituted by halogen, C₁ -C₄alkyl or by C₁ -C₄ alkoxy, or phenyl or benzyl each of which isunsubstituted or substituted by halogen, C₁ -C₄ alkyl, C₁ -C₄ alkoxy,nitro or cyano, with a halogenating agent;

the process for the preparation of a bisulfite adduct of formula##STR21## in which X is halogen and Y is a cation equivalent of analkali metal or alkaline earth metal ion, which comprises

(b) reacting a 1,2,4-trihalobutyl ether of formula ##STR22## in which Xis halogen and R₂ is unsubstituted or halo-substituted C₁ -C₁₀ alkyl, C₃-C₆ -cycloalkyl that is unsubstituted or substituted by halogen, C₁ -C₄alkyl or by C₁ -C₄ alkoxy, or phenyl or benzyl each of which isunsubstituted or substituted by halogen, C₁ -C₄ alkyl, C₁ -C₄ alkoxy,nitro or cyano, with an aqueous bisulfite solution;

and the process for the preparation of cyclopropanecarbaldehydes offormula ##STR23## in which R₁ is C₁ -C₄ alkyl or benzyl, which comprises

(c) cyclising a bisulfite adduct of formula ##STR24## in which X ishalogen and Y is a cation equivalent of an alkali metal or alkalineearth metal ion, in the presence of a base, with a thiolate of formula

    R.sub.1 --S.sup.⊖ Z.sup.⊕                      (V)

in which R₁ is C₁ -C₄ alkyl or benzyl and Z is a cation equivalent of analkali metal or alkaline earth metal ion, to form acyclopropanecarbaldehyde of formula I.

In the definitions used in this description, the generic terms used haveespecially the following individual meanings:

Alkyl is methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl,sec-butyl or tert-butyl, or an isomeric pentyl, hexyl, heptyl, octyl,nonyl or decyl radical. Where R₂ is alkyl, C₁ -C₄ alkyl is preferred.

Halogen is fluorine, chlorine, bromine or iodine, especially chlorine orbromine.

Alkali metal and alkaline earth metal ions are especially lithium,sodium, potassium and also the divalent ions of magnesium and calcium.In the case of the bisulfite adducts the sodium and potassium salts arepreferred, with the sodium salts being more especially preferred.

Haloalkyl as a meaning of the substituent R₂ is especially2-chloroethyl, 2-chloropropyl, 2-chlorobutyl or 4-chlorobutyl.

Cycloalkyl is cyclopropyl, cyclobutyl, cyclopentyl or cyclohexyl,preferably cyclopentyl or cyclohexyl. The cycloalkyl radicals may inturn be substituted by halogen, alkyl or alkoxy. Preferably, thecycloalkyl radicals are unsubstituted or are substituted by up to threeidentical or different substituents from halogen, C₁ -C₄ alkyl and C₁-C₄ alkoxy.

R₂ as phenyl or benzyl is preferably unsubstituted, but can also besubstituted by up to three identical or different substituents fromhalogen, C₁ -C₄ alkyl, C₁ -C₄ alkoxy, nitro and cyano. R₂ as alkyl ispreferably unsubstituted C₁ -C₄ alkyl.

In the case of the two-step or the three-step process (combination ofProcess Steps (b)+(c); (a)+(b); or (a)+(b)+(c)) the syntheses mayadvantageously be carried out as "one-pot processes", that is to saywithout isolation of the respective intermediates.

The following features have proved advantageous for the individualProcess Steps:

Process Step (a)

The halogenation of the tetrahydrofuran II is carried out successfullyin the presence of from 0.005 to 0.5 mol of a catalyst, optionally withfrom 0.0001 to 0.5 mol of a proton donor, from 1 to 6 mol of thehalogenating agent and from 0 to 200 ml of an inert solvent per mol ofeduct. Suitable proton donors are, for example, water, alcohols, acids,such as hydrochloric acid, sulfuric acid, carboxylic acids and sulfonicacids, and ammonium ions (with the exception of quaternary ammoniumions). Preferred proton donors are water, alcohols and hydrochloricacid. In an especially advantageous manner, Process Step (a) is carriedout without a solvent in the presence of from 0.02 to 0.1 mol of acatalyst, optionally with from 0.001 to 0.01 mol of water, and from 1.10to 1.15 mol of halogenating agent.

Especially preferred are those halogenating agents of which the residuescan be removed from the reaction mixture easily owing to their readyvolatility, such as, for example, thionyl chloride or thionyl bromide.Thionyl chloride is particularly suitable.

There may be mentioned as catalysts especially aromatic amines, such aspyridine, lutidine, 4-dimethylaminopyridine, quinoline, picoline,tertiary amines, such as N,N-dimethylaniline,4-N',N'-dimethylaminopyridine or 1,4-diazabicyclo[2.2.2]octane, and alsotrialkylamines, such as triethylamine or ethyldiisopropylamine, oramides, such as dimethylformamide, dimethylacetamide orhexamethylphosphorus triamide.

Suitable solvents are, inter alia, aromatic hydrocarbons, such astoluene, xylene or benzene; ethers, such as tetrahydrofuran, dioxane,diethyl ether or diisopropyl ether; alicyclic or aliphatic hydrocarbons,such as cyclohexane, hexane or higher-boiling alkanes; chlorinatedhydrocarbons, such as dichloromethane or trichloromethane.

The process is preferably carried out at temperatures of from roomtemperature to approximately 140° C., especially in a range of from 30°to 100° C. and more especially from 80° to 85° C.

In an especially preferred form, the process is carried out at theboiling temperature of the reaction mixture in the presence of from 0.02to 0.1 mol of pyridine or triethylamine as catalyst, from 1.10 to 1.15mol of thionyl chloride, and without a solvent. In this advantageousform of Process Step (a), the product obtained is a1,4-dichloro-2-halobutyl ether of formula ##STR25## in which X ishalogen and R₂ is unsubstituted or halo-substituted C₁ -C₁₀ alkyl, C₃-C₆ cycloalkyl that is unsubstituted or substituted by halogen, C₁ -C₄alkyl or by C₁ -C₄ alkoxy, or phenyl or benzyl each of which isunsubstituted or substituted by halogen, C₁ -C₄ alkyl, C₁ -C₄ alkoxy,nitro or cyano.

Process Step (b)

The hydrolysis of the ether III to form the bisulfite adduct IV isadvantageously carried out in an aqueous two-phase system undercontrolled pH conditions. When using a 40% sodium bisulfite solution, inparticular the following preferred and especially preferred ratios ofsolvents and educts come into consideration:

Preferred are from 1.0 to 2.0 mol of sodium bisulfite (in the form of a40% aqueous solution), from 20 to 200 ml of water and from 20 to 200 mlof an inert organic solvent per mol of ether III. Especially preferredare from 1.0 to 1.1 mol of sodium bisulfite (in the form of a 40%aqueous solution), from 40 to 60 ml of water and from 40 to 60 ml oforganic solvent per mol of ether III.

The reaction is advantageously carried out at temperatures of from 0° to100° C., and preferably at temperatures of from 30° to 80° C.

The pH value of the reaction mixture is maintained in a range ofapproximately from 2 to 7, preferably from 3.0 to 3.5, by the controlledaddition of a base. NaOH or KOH (for example in the form of a 30%aqueous solution) are suitable as bases.

Preferably, an ether of formula IIIa is used for carrying out ProcessStep (b).

The solvents suitable for Process Step (b) correspond to those mentionedin Step (a). In addition, esters such as, for example, ethyl acetate,are suitable. Toluene is especially preferred.

The bisulfite adduct obtainable by Process Step (b) can be obtained in asimple manner by first of all gently heating the reaction mixture andremoving the organic phase at that elevated temperature. The product IVcrystallises from the aqueous phase in a high degree of purity and caneither be separated off, or directly further processed in Process Step(c) in the form of an aqueous suspension.

Process Step (c)

The bisulfite adduct IV is suspended in from 400 to 1000 ml, preferablyfrom 600 to 800 ml, of water per mol of educt, or the suspensionobtainable in accordance with Process Step (b) is used directly. Attemperatures of from -20° to +40° C., preferably from 0° to 5° C., from1.0 to 1.5 mol, preferably from 1.0 to 1.05 mol, of thiolate V are addedthereto. The reaction mixture is adjusted to a basic pH value with from1.02 to 2.20 mol, preferably from 1.02 to 2.0 mol, of sodium hydroxidesolution. The product can then be extracted from the reaction mixture.

For carrying out Process Step (c), bisulfite adducts of formula##STR26## in which X is halogen and Y is a cation equivalent of analkali metal or alkaline earth metal ion are especially preferred.

Preferred thiolates are the sodium and potassium thiolates of formula V.

Apart from sodium hydroxide solution, other alkali metal and alkalineearth metal hydroxides or carbonates may be used as bases in theafore-mentioned Reaction Steps (b) and (c).

The process according to the invention is distinguished by numerousadvantages as compared with that known from the prior art. It usesreadily available educts and reagents. Carrying out the reaction isuncomplicated (temperature, solvents, pH control, the use of water asreaction medium, isolation of the products, good removal of theby-products and residues etc.). The process can be carried out with orwithout isolation of the intermediates. The bisulfite adduct IV isstable in storage. In addition, the process has a high yield and highproduct quality in every single reaction step.

The following Examples illustrate the invention.

PREPARATORY EXAMPLES P.1. Preparation of(1,2,4-trichlorobut-1-yl)-methyl ether

130.9 g (1.1 mol) of thionyl chloride are added dropwise at from 80° to85° C., over a period of 2 hours, to 136.5 g (1.0 mol) of3-chloro-2-methoxytetrahydrofuran and 1.58 g (0.02 mol) of pyridine,evolution of gas occurring immediately. The reaction mixture is furtherstirred until the evolution of gas has ceased, and is then cooled toroom temperature.

185.7 g (97%) of the title compound of formula ##STR27## are isolated inthe form of a light-brown liquid (Comp. No. 1.01).

    ______________________________________                                        Spectroscopic data for ocmpound No. 1.01:                                     .sup.1 H-NMR (90 MHz, CDCl.sub.3):                                            ppm       Identification                                                      ______________________________________                                        1.9-2.9   multiplet 2H--C(3)                                                  3.4-4.0   multiplet 2H--C(4)                                                  3.63      singlet H.sub.3 C--O                                                4.1-4.6   multiplet H--C(2)                                                   4.68 and 4.76                                                                           2 doublets, ratio 1:2, J = 7 and J = 4 H--C(1)                      ______________________________________                                    

MS: 157(10), 155(16), 121(2), 119(7), 107(3), 105(10), 94(2), 92(5),81(34), 79(100), 55(3), 53(5), 51(13); M=191.5; (for bothdiastereoisomers).

The compounds of Table I can be prepared analogously (using SOCl₂ orSOBr₂ as halogenating agent).

                  TABLE I                                                         ______________________________________                                        Compounds of formula                                                           ##STR28##                    (III)                                           Comp. No.                                                                             X'     X"     X'"  R.sub.2                                                                            B.p./pressure                                                                            Yield                              ______________________________________                                        1.01    Cl     Cl     Cl   CH.sub.3                                                                           +100° C./5.3 Pa                                                                     97%                              1.02    Br     Cl     Br   CH.sub.3                                           1.03    Br     Br     Br   CH.sub.3                                           1.04    Cl     Br     Cl   CH.sub.3                                                                            +85° C./2.7 Pa                                                                   96.8%                              1.05    Cl     Cl     Cl   C.sub.2 H.sub.5                                    1.06    Br     Cl     Br   C.sub.2 H.sub.5                                    1.07    Br     Br     Br   C.sub.2 H.sub.5                                    1.08    Cl     Br     Cl   C.sub.2 H.sub.5                                    ______________________________________                                    

P.2. Preparation of the bisulfite adducts IV

P.2.1. Preparation of the bisulfite adduct of 2,4-dichlorobutyraldehyde

185.6 g (0.97 mol) of (1,2,4-trichlorobut-1-yl)-methyl ether are addeddropwise at from 40° to 45° C., over a period of one hour, to 310.0 g(1.0 mol) of a 33.5% aqueous sodium hydrogen sulfite solution and 50 mlof toluene. At the same time the pH value is maintained at from 3.0 to3.5 with 30% aqueous NaOH solution. The reaction mixture is then heatedto from 70° to 75° and the toluene phase is removed and discarded. Theproduct crystallises out on cooling the aqueous phase to 15° C.

162.1 g (66%) of the title compound of formula ##STR29## are isolated inthe form of a colourless powder (Comp. No. 2.01).

By recrystallisation of the mother liquors it is possible to isolate afurther 58.2 g (23.7%) of the title compound.

P.2.2. Preparation of the bisulfite adduct of 2,4-dichlorobutyraldehydefrom 3-chloro-2-methoxytetrahydrofuran (II)

P.2.2.1. Using triethylamine as catalyst: 13.1 g (110 mmol) are addeddropwise at from 80° to 85° C., over a period of 2 hours, to 13.6 g (100mmol) of 3-chloro-2-methoxytetrahydrofuran and 0.2 g (2 mmol) oftriethylamine. The (1,2,4-trichlorobut-1-yl)-methyl ether obtainable inthis manner is added over a period of 30 minutes at from 40° to 45° C.to 31.0 g (100 mmol) of a 33.5% aqueous sodium hydrogen sulfite solutionand 6 ml of toluene, the pH value of the reaction mixture being held atfrom 3.0 to 3.5 with 30% NaOH solution. The reaction mixture is thenheated to from 70° to 75° C., the toluene phase is removed and theaqueous phase is cooled to room temperature, the product precipitating.

68.3 g (94.8%) of the title compound of formula ##STR30## are isolatedin the form of a 34% aqueous suspension (Comp. No. 2.01).

P.2.2.2. Using lutidine as catalyst: Analogously to Example P.2.2.1.,66.1 g (91.7%) of the title compound of formula ##STR31## in the form ofa 34% aqueous bisulfite adduct suspension (Comp. No. 2.01) are obtainedfrom 13.6 g (100 mmol) of 3-chloro-2-methoxytetrahydrofuran, 0.1 g (2mmol) of lutidine and 13.1 g (110 mmol) of thionyl chloride, 31.0 g (100mmol) of 33.5% aqueous sodium bisulfite solution and 6 ml of toluene.

¹ H-NMR (360 MHz, D₂ O): δ=2.1-2.45 and 2.5-2.65 (2 m, 2H-C(3));3.7-3.95 (m, 2H-C(4)); 4.55-4.9 (3 complex signals, H-C(1) and H-C(2)).

The compounds of Table II are obtained analogously to the P.2.Preparatory Examples.

                  TABLE II                                                        ______________________________________                                        Compounds of formula                                                           ##STR32##                                                                    Comp. No.     X'       X"    Yield [%]                                        ______________________________________                                        2.01          Cl       Cl    95                                               2.02          Br       Cl                                                     2.03          Br       Br                                                     2.04          Cl       Br    90 (1)                                           ______________________________________                                         (1) from 3bromo-2-methoxytetrahydrofuran with SOCl.sub.2 as halogenating      agent and pyridine as catalyst.                                          

P.3. Preparation of the cyclopropanecarbaldehydes I

P.3.1. 1-methylthiocyclopropanecarbaldehyde

42.8 g (175 mmol) of 2,4-dichlorobutyraldehyde bisulfite adduct(suspended in 200 ml of water) are added dropwise at from 0° to 5° C.,over a period of one hour, to 98.5 g (225 mmol) of a 16% aqueous sodiummethyl thiolate solution and 60.0 g (450 mmol) of a 30% aqueous sodiumhydroxide solution. The mixture is stirred for a further 45 minutes andthen 100 ml of dichloromethane are added and the aqueous phase isseparated off. The organic phase is concentrated by evaporation in vacuo(50° C./500 mbar) in a rotary evaporator.

19.4 g (95.6%) of the title compound of formula ##STR33## (Compound No.4.01) are isolated.

The compounds of Table III are isolated in an analogous manner.

                                      TABLE III                                   __________________________________________________________________________    Example                                                                            Educt          R.sub.1 S.sup.⊖ Na.sup.⊕                                                   Product      Yield                               __________________________________________________________________________    P.3.1.2.                                                                            ##STR34##     CH.sub.3 SNa                                                                            ##STR35##                                       P.3.1.3.                                                                            ##STR36##     CH.sub.3 SNa                                                                            ##STR37##   90%                                 P.3.1.4.                                                                            ##STR38##     CH.sub.3 SNa                                                                            ##STR39##                                       P.3.1.5.                                                                            ##STR40##     CH.sub.3 (CH.sub.2).sub.3 SNa                                                           ##STR41##   69%                                 P.3.1.6.                                                                            ##STR42##     C.sub.6 H.sub.5CH.sub.2 SNa                                                             ##STR43##   58%                                 __________________________________________________________________________

P.3.2. 1-methylthiocyclopropanecarbaldehyde from3-chloro-2-methoxytetrahydrofuran without isolation of the intermediates

273.0 g (2.0 mol) of 3-chloro-2-methoxytetrahydrofuran, 3.16 g (40 mmol)of pyridine, 261.8 g (2.2 mol) of thionyl chloride, 620 g (2.0 mol) of33.5% of aqueous sodium hydrogen sulfite solution and 100 ml of tolueneare reacted analogously to Example P.2.2. to form an aqueous suspensionof the 2,4-dichlorobutyraldehyde bisulfite adduct. The aqueoussuspension obtainable in this manner is diluted with 210 ml of water andcooled to 0° C. 876.3 g (2.0 mol) of a 16% sodium methyl thiolatesolution and 533.0 g (4.0 mol) of a 30% aqueous sodium hydroxidesolution are then added dropwise over a period of 3 hours at from 0° to5° C. The mixture is then stirred for a further 45 minutes at from 0° to5° C., heated to room temperature, extracted with toluene ordichloromethane, the aqueous phase is separated off and the organicphase is concentrated in vacuo in a rotary evaporator.

185.7 g (80%) of the title compound of formula ##STR44## (Comp. No.4.01) are isolated.

The compounds of Table IV can be prepared analogously to the abovePreparatory Examples:

                  TABLE IV                                                        ______________________________________                                        Compounds of formula                                                           ##STR45##                     (I)                                            Comp. No.                                                                             R.sub.1     Boiling point/pressure                                                                         Yield                                    ______________________________________                                        4.01    CH.sub.3    +91 to +92° C./10000 Pa                                                                 80%                                      4.02    CH.sub.3 (CH.sub.2).sub.3    61%                                      4.03    C.sub.6 H.sub.5CH.sub.2                                                                   +90 to +91° C./1.3 Pa                                                                   51%                                      4.04    C.sub.2 H.sub.5                                                                           +57 to +58° C./1800 Pa                             4.05    C.sub.3 H.sub.7 -n                                                                        +74 to +76° C./2000 Pa                             4.06    C.sub.3 H.sub.7 -i                                                                        +67 tp +68° C./2000 Pa                             ______________________________________                                    

What is claimed is:
 1. A process for the preparation of cyclopropanecarbaldehydes of formula ##STR46## in which R₁ is C₁ -C₄ alkyl or benzyl, which comprises (a) reacting a tetrahydrofuran of formula ##STR47## in which X is halogen and R₂ is unsubstituted or halo-substituted C₁ -C₁₀ alkyl, C₃ -C₆ cycloalkyl that is unsubstituted or substituted by halogen, C₁ -C₄ alkyl or by C₁ -C₄ alkoxy, or phenyl or benzyl each of which is unsubstituted or substituted by halogen, C₁ -C₄ alkyl, C₁ -C₄ alkoxy, nitro or cyano, with a halogenating agent to form a 1,2,4-trihalobutyl ether of formula ##STR48## in which X is halogen and R₂ is unsubstituted or halo-substituted C₁ -C₁₀ alkyl, C₃ -C₆ cycloalkyl that is unsubstituted or substituted by halogen, C₁ -C₄ alkyl or by C₁ -C₄ alkoxy, or phenyl or benzyl each of which is unsubstituted or substituted by halogen, C₁ -C₄ alkyl, C₁ -C₄ alkoxy, nitro or cyano, and(b) then reacting the compound of formula III with an aqueous bisulfite solution to form a bisulfite adduct of formula ##STR49## in which X is halogen and Y is a cation equivalent of an alkali metal or alkaline earth metal ion, and (c) then cyclising the adduct, in the presence of a base, with a thiolate of formula

    R.sub.1 --S.sup.⊖ Z.sup.⊕                      (V)

in which R₁ is C₁ -C₄ alkyl or benzyl and Z is a cation equivalent of an alkali metal or alkaline earth metal ion, to form a cyclopropanecarbaldehyde of formula I.
 2. A process for the preparation of cyclopropanecarbaldehydes of formula ##STR50## in which R₁ is C₁ -C₄ alkyl or benzyl, which comprises (a) reacting a tetrahydrofuran of formula ##STR51## in which X is halogen and R₂ is unsubstituted or halo-substituted C₁ -C₁₀ alkyl, C₃ -C₆ cycloalkyl that is unsubstituted or substituted by halogen, C₁ -C₄ alkyl or by C₁ -C₄ alkoxy, or phenyl or benzyl each of which is unsubstituted or substituted by halogen, C₁ -C₄ alkyl, C₁ -C₄ alkoxy, nitro or cyano, with thionyl chloride to form a 1,4-dichloro-2-halobutyl ether of formula ##STR52## in which X is halogen and R₂ is unsubstituted or halo-substituted C₁ -C₁₀ alkyl, C₃ -C₆ cycloalkyl that is unsubstituted or substituted by halogen, C₁ -C₄ alkyl or by C₁ -C₄ alkoxy, or phenyl or benzyl each of which is unsubstituted or substituted by halogen, C₁ -C₄ alkyl, C₁ -C₄ alkoxy, nitro or cyano, and(b) then reacting the compound of formula IIIa with an aqueous bisulfite solution to form a bisulfite adduct of formula ##STR53## in which X is halogen and Y is a cation equivalent of an alkali metal or alkaline earth metal ion, and (c) then cyclising the adduct, in the presence of a base, with a thiolate of formula

    R.sub.1 --S.sup.⊖ Z.sup.⊕                      (V)

in which R₁ is C₁ -C₄ alkyl or benzyl and Z is a cation equivalent of an alkali metal or alkaline earth metal ion, to form a cyclopropanecarbaldehyde of formula I.
 3. A process for the preparation of cyclopropanecarbaldehydes of formula ##STR54## in which R₁ is C₁ -C₄ alkyl or benzyl, which comprises (b) reacting a 1,2,4-trihalobutyl ether of formula ##STR55## in which X is halogen and R₂ is unsubstituted or halo-substituted C₁ -C₁₀ alkyl, C₃ -C₆ cycloalkyl that is unsubstituted or substituted by halogen, C₁ -C₄ alkyl or by C₁ -C₄ alkoxy, or phenyl or benzyl each of which is unsubstituted or substituted by halogen, C₁ -C₄ alkyl, C₁ -C₄ alkoxy, nitro or cyano, with an aqueous bisulfite solution to form a bisulfite adduct of formula ##STR56## in which X is halogen and Y is a cation equivalent of an alkali metal or alkaline earth metal ion and(c) subsequently cyclising the adduct, in the presence of a base, with a thiolate of formula

    R.sub.1 --S.sup.⊖ Z.sup.⊕                      (V)

in which R₁ is C₁ -C₄ alkyl or benzyl and Z is a cation equivalent of an alkali metal or alkaline earth metal ion, to form a cyclopropanecarbaldehyde of formula I.
 4. A process according to claim 3 which comprises(b) reacting a 1,4-dichloro-2-halobutyl ether of formula ##STR57## in which X is halogen and R₂ is unsubstituted or halo-substituted C₁ -C₁₀ alkyl, C₃ -C₆ cycloalkyl that is unsubstituted or substituted by halogen, C₁ -C₄ alkyl or by C₁ -C₄ alkoxy, or phenyl or benzyl each of which is unsubstituted or substituted by halogen, C₁ -C₄ alkyl, C₁ -C₄ alkoxy, nitro or cyano, with an aqueous bisulfite solution to form a bisulfite adduct of formula ##STR58## in which X is halogen and Y is a cation equivalent of an alkali metal or alkaline earth metal ion and (c) subsequently cyclising the adduct, in the presence of a base, with a thiolate of formula

    R.sub.1 --S.sup.⊖ Z.sup.⊕                      (V)

in which R₁ is C₁ -C₄ alkyl or benzyl and Z is a cation equivalent of an alkali metal or alkaline earth metal ion, to form a cyclopropanecarbaldehyde of formula I.
 5. A process for the preparation of a bisulfite adduct of formula ##STR59## in which X is halogen and Y is a cation equivalent of an alkali metal or alkaline earth metal ion, which comprises(a) reacting a tetrahydrofuran of formula ##STR60## in which X is halogen and R₂ is unsubstituted or halo-substituted C₁ -C₁₀ alkyl, C₃ -C₆ cycloalkyl that is unsubstituted or substituted by halogen, C₁ -C₄ alkyl or by C₁ -C₄ alkoxy, or phenyl or benzyl each of which is unsubstituted or substituted by halogen, C₁ -C₄ alkyl, C₁ -C₄ alkoxy, nitro or cyano, with a halogenating agent to form a 1,2,4-trihalobutyl ether of formula ##STR61## in which X is halogen and R₂ is unsubstituted or halo-substituted C₁ -C₁₀ alkyl, C₃ -C₆ cycloalkyl that is unsubstituted or substituted by halogen, C₁ -C₄ alkyl or by C₁ -C₄ alkoxy, or phenyl or benzyl each of which is unsubstituted or substituted by halogen, C₁ -C₄ alkyl, C₁ -C₄ alkoxy, nitro or cyano, and (b) then reacting the compound of formula III with an aqueous bisulfite solution to form the bisulfite adduct of formula IV.
 6. A process for the preparation of 1,2,4-trihalobutyl ethers of formula ##STR62## in which X is halogen and R₂ is unsubstituted or halo-substituted C₁ -C₁₀ alkyl, C₃ -C₆ cycloalkyl that is unsubstituted or substituted by halogen, C₁ -C₄ alkyl or by C₁ -C₄ alkoxy, or phenyl or benzyl each of which is unsubstituted or substituted by halogen, C₁ -C₄ alkyl, C₁ -C₄ alkoxy, nitro or cyano, which comprises(a) reacting a tetrahydrofuran of formula ##STR63## in which X is halogen and R₂ is unsubstituted or halo-substituted C₁ -C₁₀ alkyl, C₃ -C₆ cycloalkyl that is unsubstituted or substituted by halogen, C₁ -C₄ alkyl or by C₁ -C₄ alkoxy, or phenyl or benzyl each of which is unsubstituted or substituted by halogen, C₁ -C₄ alkyl, C₁ -C₄ alkoxy, nitro or cyano, with a halogenating agent.
 7. A process for the preparation of a bisulfite adduct of formula ##STR64## in which X is halogen and Y is a cation equivalent of an alkali metal or alkaline earth metal ion, which comprises(b) reacting a 1,2,4-trihalobutyl ether of formula ##STR65## in which X is halogen and R₂ is unsubstituted or halo-substituted C₁ -C₁₀ alkyl, C₃ -C₆ cycloalkyl that is unsubstituted or substituted by halogen, C₁ -C₄ alkyl or by C₁ -C₄ alkoxy, or phenyl or benzyl each of which is unsubstituted or substituted by halogen, C₁ -C₄ alkyl, C₁ -C₄ alkoxy, nitro or cyano, with an aqueous bisulfite solution.
 8. A process for the preparation of cyclopropanecarbaldehydes of formula ##STR66## in which R₁ is C₁ -C₄ alkyl or benzyl, which comprises (c) cyclising a bisulfite adduct of formula ##STR67## in which X is halogen and Y is a cation equivalent of an alkali metal or alkaline earth metal ion, in the presence of a base, with a thiolate of formula

    R.sub.1 --S.sup.⊖ Z.sup.⊕                      (V)

in which R₁ is C₁ -C₄ alkyl or benzyl and Z is a cation equivalent of an alkali metal or alkaline earth metal ion, to form a cyclopropanecarbaldehyde of formula I. 